Washington  Having established a fast-charging foothold in California for its electric cars, Tesla Motors has brought its formula east, opening two ultrafast charging stations in December that would, in theory, allow a speedy electric-car road trip between here and Boston.

But as I discovered on a recent test drive of the companys high-performance Model S sedan, theory can be trumped by reality, especially when Northeast temperatures plunge

It appears to be on the order of 85,000 - based on their claimed one hour charge. That’s still too low. A gas pump pushing unleaded can do the equivalent of 1,000,000 - which is why you can fill up in 5 minutes.

I think you give him too much credit. I think Obama is totally ignorant of matters scientific. Remember: this is a guy who has never really practiced law, so he has no practical knowledge of anything tangible, except politics.

Just because the guys knows something about physics, doesnt mean he knows anything about this particular problem. Remember, it was not professor Langley was first flew, but two mechanics in a bike-shop in Ohio who figured out the principles of flight using gliders.The they cobbled together the first plane by attached an internal combustion motor to the frame and a propellor to push the thing. Orville was the brother who really figure out how to make the contraption work. But I must say that the Wright brothers did more to master aerodynamics than any of the scientists who worked on the problem. These guys were much more than tinkerers. They deserved a Nobel prize for physics.

Just because the guys knows something about physics, doesnt mean he knows anything about this particular problem. Remember, it was not professor Langley was first flew, but two mechanics in a bike-shop in Ohio who figured out the principles of flight using gliders.The they cobbled together the first plane by attached an internal combustion motor to the frame and a propellor to push the thing. Orville was the brother who really figure out how to make the contraption work. But I must say that the Wright brothers did more to master aerodynamics than any of the scientists who worked on the problem. These guys were much more than tinkerers. They deserved a Nobel prize for physics.

Volt amps is a measurement of power, not energy. You don't store volt-amps, you store watt-hours.

It's power that kills, not energy. I can swim in a large river with no harm. But a river is full of power (kinetic energy of millions of tons of moving water. Transfer of that energy into my mody is insignificant. Similarly, I can climb a mountain and live there for years with no damage. But a body high above ground has potential energy; I won't see even a joule of it unless I fall into an abyss. Measuring energy is only important if you are building a battery-powered machine and want to know for how long it will work. We already know that an EV will kill at least one man without much drain on the battery; counting past that is not productive.

Electric power kills by two most obvious methods and by several less obvious ones. The main injury comes from interference with your nervous system. A light shock can desynchronize the heart, and you are done for in a few minutes. Then the thermal effect of the current heats the tissue up; skin burns, muscles cook. Among less obvious effects is the involuntary muscle contraction that can cause you to injure yourself. I'm not an expert on safety, but I sat through a short, formal course many moons ago.

Typically the damage is proportional to the current, not to the voltage. A 25 kV zap from a TV tube anode may not kill you, unless you try hard. At the same time even 48V can kill you if you fall onto bus bars and break the skin. The majority of insulation is in the skin; everything else is very conductive, like a bag of salty water that we are.

An EV or a hybrid is pretty dangerous because of two factors. First, it has voltages high enough to punch through the upper layers of skin. There is a considerable nonlinearity there, as with all dielectrics near their breakdown voltage. Second, once the channel is established the EV can deliver current that can kill a whole herd of elephants. If you are a witness of an EV crash and want to help, you must walk very carefully, watch your step, bypass puddles of conductive liquids, and operate with one arm only (the other must be behind your back at all times) - and still you must watch your shoes because the return path will be through the ground. Best if you don't touch anything at all and use an isolating pole; but chances of you having one are near zero, unless you can flag down a utility truck. Those guys usually have safety equipment and can do the job easily; they are trained on all that and they regularly work on transmission lines that are far worse. Firefighters are also aware of electricity because they deal with household voltages every day and with higher ones whenever a transformer blows up.

I understand the concept very well. I am an electrical engineer specialized in power systems.

But the original poster asked:

How many volt-amps are they trying put in these cars?

They were asking about storage while using the measurement of delivery.

Typically the damage is proportional to the current, not to the voltage.

The current is going to be determined by the voltage, and the impedance (resistance) of the system which includes the body parts in the circuit as well as the connection to return path of current, typically involving the ground.

As the check out people at Trader Joes are bagging my groceries in plastic per my request, I use the opportunity to point out to them that 85 plastic bags can be recycled for the energy it takes to recycle one paper one.

70
posted on 02/10/2013 7:43:08 PM PST
by Hoodat
("As for God, His way is perfect" - Psalm 18:30)

Thank you, thackney. The meaning of the word "power" is understood by few people. It is rarely used correctly in articles, even those written by people who should know better. This even happens in text books, since the word is difficult to use correctly.Power is a rate. It can't be made, used, stored, or sold. Power companies don't make power. You don't pay your power bill.

Most people think power is energy. It is common to hear people say something produces so many watts per hour.

thackney, I know you know this, but for those who don't, power is the amount energy converted from one form to another in a given time. Energy is measured in joules. Power is measured in joules per second. A watt is a joule per second. Therefore, energy can be calculated by multiplying power times time.

Someone who does not know this produces confusing questions and comments. It requires care to use the word 'power' correctly. When in doubt, use joules per second instead of watts. Use joules for energy.

71
posted on 02/11/2013 2:39:07 AM PST
by Right Wing Assault
(Dick Obama is more inexperienced now than he was before he was elected.)

Plastic bags also take up one-seventh of the landfill space that a paper bag takes up.

Back in the 70s, the enviro-nazis were demanding things that would break down into simpler compounds once placed in landfills. Two decades later, they learned that these simpler compounds they had demanded were now leaching into our water supply. Idiots. So yes, locking up carbon in landfills would be the logical approach. But logic simply isn't their strong suit.

73
posted on 02/11/2013 2:54:51 AM PST
by Hoodat
("As for God, His way is perfect" - Psalm 18:30)

Yea, I saw an interview with him. He basically says the NY Times didn’t give the whole story and the guy was driving 10 over the speed limit and then went through Manhattan. But he also didn’t comment on the overnight energy loss that led to the lockup near the end of the drive.

But yes, it is interesting. The NY Times isn’t used to being “fact-checked”.

That’s because the electro-chemical reactions in a battery can’t be made to scale like the size of gates on a wafer. Too many people keep thinking that all the strides we made in chip gate density are mirrored in other aspects of electrical engineering.

We’re not going to see any huge breakthroughs in battery power density without some huge breakthrough in physics and chemistry. The barrier to huge energy densities isn’t within the power of us EE’s to fix - it’s something that’s going to require real ground-level science research to achieve, as you indicate.

This entire scam shows the public ignorance of the difference between a scientist and an engineer. They’re not the same. The Obama administration, being staffed with a bunch of Ivy League, liberal arts academics... can’t see the difference. Which is why we’re pouring money down ratholes that need to be plugged with blue-sky research...

Funny think about science fiction is that its writers can tell us what we CANNOT do by inventing things that are far beyond our physics. There is an old 50s movie with Rex Reason, where he holds up what looks sort of life a large sparkplug and which is supposes to be an energy-generator whose total output is equal to the total of electric power generated on the whole earth. he carefully explains the eeed for this sort of thing. As you suggest, we need to learn the principle underlying such a gizmo to produce the right size batteries. He have not, and it takes magical thinking to believe we can do without it.

It takes a great scientist to know the limits of science. Dick Feynman had the instincts of an EE matched with the ingenuity of a Willie Sutton, and an intuitive grasp of mathematics. A kind of magus, you know. Any, in his little book, Surely you are joking, he talks about trying to explain modern physics to his Dad—a really smart guy. Try as he would, he could not. So I am not sure that these liberal arts types will ever get what needs to be before they can build their fairy castles in the air.

It takes a great scientist to know the limits of science. Dick Feynman had the instincts of an EE matched with the ingenuity of a Willie Sutton, and an intuitive grasp of mathematics. A kind of magus, you know. Anyway, in his little book, Surely you are joking, he talks about trying to explain modern physics to his Dad—a really smart guy. Try as he would, he could not. So I am not sure that these liberal arts types will ever get what needs to be before they can build their fairy castles in the air.

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